Cartridge, a piston and a syringe comprising the cartridge and the piston

ABSTRACT

A cartridge and a piston for storing and dispensing a two-component dental material. The cartridge and the piston have a cross-section which substantially correspond to a D-shape in which the perimeter of the D-shape is defined by a plurality of circle segments only. At least two of the circle segments are based on different radii. The invention helps maximizing the time period over which a dental material can be stored in the compartment.

FIELD OF THE INVENTION

The invention relates to a cartridge, a piston and a syringe comprisingsuch a cartridge and piston. In particular the invention relates to anew substantial D-shape for the cross-sections of cartridge compartmentsand corresponding pistons cooperating with such compartments. Suchsubstantial D-shape is particularly defined by a plurality of circlesegments only.

BACKGROUND ART

Dental materials are often stored in packages from which they can bedirectly dispensed to a desired location. For example the dentalmaterials may be dispensed from the package on a pad or into a well andfrom there applied within a patient's mouth. In other situations thedental materials may be placed into a patient's mouth directly from sucha package.

Dental materials further are often prepared from two or more componentsthat are mixed together just before use. Often the individual componentsare obtained as portions from larger packages, for example from tubes,bags or cartridges. There are packages on the market that allow manualor automatic dispensing of two or more components at desired amounts andat an appropriate ratio for mixing. Furthermore there are packages thatallow dispensation of portions of readily mixed materials fromindividually stored components.

Often double-barrel syringes are used for storing and mixingtwo-component dental materials. Such double-barrel syringes typicallyhave two side by side tubular barrels from which the components of thedental material can be extruded by pushing pistons into the respectivebarrel. In one configuration of such a double-barrel syringe hasD-shaped barrels which, arranged side by side, overall form onecylindrical structure as disclosed for example in U.S. Design Pat. No.362,722.

-   provide a syringe which is relatively compact and easy to use, but    which further provides a relatively long shelf-life for the    components stored therein.

SUMMARY OF THE INVENTION

The invention concerns in one aspect a cartridge for storing anddispensing a two-component dental material. The cartridge comprises twocompartments each extending within the cartridge at a cross-sectionwhich substantially corresponds to a D-shape. The perimeter of theD-shape is defined by a plurality of circle segments only. Further atleast two of the circle segments are based on or have different radii.Each of the different radii are definite.

For the purpose of the present invention a “circle segment” isunderstood as a technical term having a definite radius. The circlesegment particularly differs technically from a straight line which onlymathematically may be defined as a circle having an indefinite radius.

The invention is advantageous in that it helps maximizing the tightnessof a seal between the pistons and the cartridge. Further the inventionhelps maximizing the time period over which the dental material, orcomponents thereof can be stored within the cartridge closed by thepistons without the dental material substantially alters in itsproperties.

The cartridge of the invention may extend generally linear along alongitudinal axis. The cartridge preferably has an outer cylindricalshape over a major part of a cartridge length over which the cartridgeextends. The compartments may extend parallel relative to each other andparallel to the longitudinal axis. Preferably each of the compartmentsextends at a generally uniform cross-section. The two compartments arepreferably separated from each other by a separation wall of thecartridge.

In one embodiment the compartments are sized for storing the twocomponents at a volume ratio of 1:1. However in other embodiments thecompartments may be sized for storing the two components at volumeratios of 1:2, 1:3, 1:5, 1:10, or any other appropriate ratio. Suchdifferent volume ratios preferably provide respective different mixingratios of the components by use of the compartment and may beimplemented by unequally sized D-shapes of the compartmentcross-sections. circle segments together form a closed line defining theperimeter of the compartment cross-section.

In a further embodiment the circle segments join or are concatenatedsuch that respective tangents of the two circle segments through thejoint coincide. Thus the perimeter of the cross-section extends free ofany sharp edges.

In a further embodiment the perimeter of the compartment cross-sectionis defined by only four circle segments, which merge into one anotherand form a closed line. In particular the perimeter of the compartmentcross-section is preferably defined by only a first, second, third andfourth circle segment. The first and second circle segment may be basedon different radii and join at one of their ends with the third circlesegment and join on the other of their ends with the fourth circlesegment. The third and the fourth circle segment are preferably based onor have the same radius. The radius of the third and fourth circlesegment is preferably smaller than the radius of each of the first andsecond circle segment, for example, the radius of the third and fourthcircle segment may be between ⅓ and 1/10 of the radius of the secondcircle segment. Further the radius of the second circle segment ispreferably smaller than the radius of the first circle segment, forexample the radius of the second circle segment may be between ⅓ and ⅛of the radius of the first circle segment. In a preferred embodiment theradii may be as follows:

-   -   the radius of the first circle segment may be between about 10        mm and about 50 mm, preferably about 20 mm;    -   the radius of the second circle segment may be between about 2        mm and about 16 mm, preferably about 4 mm; and    -   the radius of the third and fourth circle segment may be between        about 0.3 mm and about 3 mm, preferably about 0.7 mm.        Preferably the curvature of the first, second, third and fourth        circle segment continues in the same direction, although the        magnitude of the curvature may vary in accordance to the        different radii of the first, second, third and fourth circle        segment. In other words the closed line formed of the first,        second, third and fourth circle segment preferably does not        comprise any inflection point.

-   each of the compartments for extruding one of the two components    from the cartridge. The cartridge further has a rear portion    opposite of the front portion, wherein the rear portion may be    configured to receive a piston within the compartment. In particular    the rear portion may be configured such that a piston can be    received within each of the compartments.

In a further aspect the invention relates to piston for dispensing acomponent of a dental material. The piston preferably is adapted tocooperate with the cartridge of the invention. In particular the pistonis preferably sized and shaped to slidably fit into one or any of thecompartments of the cartridge. The piston accordingly has across-section which substantially corresponds to a D-shape. The pistoncross-section as referred to herein refers to a cross-section on a planetransverse to a dimension in which the piston is movable for dispensingthe dental material. Further the perimeter of the D-shape of thepiston's cross-section is defined by a plurality of circle segmentsonly. Again at least two of the circle segments are based on or havedifferent radii.

In an embodiment the circle segments join each other at their ends suchthat all circle segments together form a closed line defining theperimeter of the compartment cross-section. The circle segmentspreferably join or are concatenated such that respective tangents of thetwo circle segments through the joint coincide.

In a further embodiment the perimeter of the piston cross-section isdefined by only four circle segments, which merge into one another andform a closed line. The perimeter of the piston cross-section ispreferably defined by only a first, second, third and fourth circlesegment, the first and second circle segment being based on differentradii and join at one of their ends with the third circle segment andjoin on the other of their ends with the fourth circle segment. Thethird and the fourth circle segment are preferably based on or have thesame radius. The radius of the third and fourth circle segment ispreferably smaller than the radius of each of the first and secondcircle segment, for example the radius of the third and fourth circlesegment may be between ⅓ and 1/10 of the radius of the second circlesegment. Further the radius of the second circle segment is preferablysmaller than the radius of the first circle segment, for example theradius of the second circle segment may be between ⅓ and ⅛ of the radiusof the first circle segment. The radii of the first, second, third andfourth circle segment of the periphery of the piston second, third andfourth circle segment of the periphery of the compartment cross-section.The offset may be between about 0.1 mm to about 0.5 mm. Hence preferredradii may be as follows:

-   -   the radius of the first circle segment may between about 10.1 mm        and about 50.5 mm, preferably about 20.1 mm;    -   the radius of the second circle segment may between about 2.1 mm        and about 16.5 mm, preferably about 4.1 mm; and    -   the radius of the third and fourth circle segment may between        about 0.4 mm and about 3.5 mm, preferably about 0.8 mm.

In a further embodiment the piston comprises a, preferably skirt-type,flexible sealing lip. The sealing lip preferably forms the outermostperimeter of the piston's cross-section. Any dimensions of the pistoncross-section as defined herein accordingly refer to outermost perimeterof the piston's cross-section. The piston may have a piston body havinga piston front side and a piston rear side. The piston front side refersto the side which is intended to face the component in the chamber,whereas the piston rear side is intended to face away from thecomponent. The sealing lip is preferably protruding from the piston bodyat the front side of the piston. It is preferred that the cross-sectionof the sealing lip increases in a direction along which the sealing lipprotrudes from the piston body. In particular in a direction along whichthe sealing lip protrudes from the piston body each of the radii of thecircle segments increases, preferably be the same offset.

In a further embodiment the cartridge contains the dental material inthe form of two components. Preferred dental materials may be selectedfrom among: dental liners, dental flowables, dental composites, dentalresin cements, dental resin modified glass ionomer cements, dentalimpression materials and dental filling materials.

In a preferred embodiment the cartridge and/or the piston is/are made ofa plastic material, in particular (high density) polypropylene,polybutadiene terephthalate, polyamide, or polyoxymethylene.

In a further aspect the invention concerns a syringe which comprises acartridge according to the invention and two pistons of the invention.The syringe may further comprise a dispensing nozzle and a static mixerarranged in the dispensing nozzle. Such a dispensing nozzle. The nozzlemay be made of polypropylene or polycarbonate.

In still a further embodiment the syringe comprising a plunger forpushing the pistons into the respective compartments for extruding thecomponents towards the dispensing nozzle. The plunger and the piston maybe formed in one piece (for example monolithically formed) or may beassembled from the two pistons and the plunger as separate parts.

The plunger may be made of (high density) polypropylene, polybutadieneterephthalate, polyamide, or polyoxymethylene. All parts of the syringemay be made by injection molding. Thus a relatively inexpensive syringemay be provided.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a syringe according to an embodiment ofthe invention;

FIG. 2 is a cross-sectional view through the syringe shown in FIG. 1

FIG. 3 is a cross-sectional view of the cartridge according to anembodiment of the invention; and

FIG. 4 is a front view on two pistons according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a syringe 1 having a cartridge 10 of the invention, aplunger 20 and a dispensing nozzle 30. The cartridge 10 of the syringe 1is pre-filled with two components of a dental material. The cartridge 10is closed at a rear portion 11 of the cartridge 10 by the plunger 20.Further the cartridge 10 has outlets (not visible in this view) whichare openably closed at a front portion 12 by the dispensing nozzle 30.In the example the front portion 12 of the cartridge 10 and thedispensing nozzle 30 in combination form a rotary slide valve. Suchrotary slide valve is adapted for a rotation between a closed position,in which the outlets of the cartridge 10 are closed by the dispensingnozzle 30, and an open position, in which the outlets are in fluidcommunication with an exit conduit 31 formed by the dispensing nozzle30. Thus in the open position the components contained in the thedispensing nozzle 30.

In the example the cartridge 10 extends at a generally cylindrical outershape. It has been found that such a shape provides for relativelyconvenient manual positioning of the syringe during operation by a user.In particular the cartridge is preferably rotatable by handling of thecartridge 10 at the cylindrical outer shape. Accordingly the cartridge10 (and thus also of the syringe 1) may be rotatably positionedrelatively easy and single-handed.

Further the cartridge in the example has a non-circular finger plate 13.Although the shape of the finger plate 13 is based on a circular shape,cutaways 14 provide for flats or supporting points which hinder thecartridge 10 in rolling over a flat surface. Thus if the syringe 1 isdisposed on a dentists tablet or table, the finger plate 13 of thecartridge 10 preferably prevents the syringe from rolling and fallingoff.

The plunger 20 has two plunger rods 21, 22 which are received at a frontend 23 of the plunger 20 within compartments (not shown) in thecartridge 10. At a rear end 24 the plunger 20 has a finger plate 25. Thefinger plate 25 allows the plunger 20 to be pushed forward by a user forextruding the dental material from the syringe 1.

FIG. 2 shows a cross-sectional view of the syringe 1 through thecartridge 10. The cartridge 10 has two compartments 15, 16 which extendthrough the cartridge 10 at a substantially D-shaped cross-section. Asshown the two substantial D-shapes are arranged in a mirrored fashionrelative to each other so that the cartridge 10 has, on the one hand, agenerally cylindrical outer shape, and on the other end forms an outerwall 17 with a separation wall 18 having a substantially uniform wallthickness. The substantially uniform wall thickness facilitates forexample manufacturing of the cartridge by injection molding.

FIG. 3 illustrates the cross-sectional shape of the cartridge 10 in moredetail. In particular the perimeter of the D-shape is defined by aplurality of circle segments 19 a, 19 b, 19 c and 19 d only. (Circlesegments 19 a, 19 b, 19 c and 19 d correspond to the first, third,second and forth circle segment, respectively.) The circle segment 19 aadjacent the separation wall is based on a different radius than theopposite circle segment 19 c adjacent the outer wall 17. In particularthe circle segment 19 a is based on a larger radius than the circlesegment 19 c. Thus, on the one hand, a substantial D-shape is achievedbut, on the having a cross-section based on only circular structuresallows more reliable sealing compared to a cross-section having one ormore straight structures. Further the circle segments 19 a, 19 b, 19 cand 19 d join in a manner such that at the joint of two circle segmentsrespective tangents through that joint on each circle segment coincide.Or in other words the circle segments 19 a, 19 b, 19 c and 19 d smoothlymerge into one another and together form a closed line defining theperimeter of the cross-section.

FIG. 4 shows a bottom view on two pistons 26, 27. Each of the twopistons 26, 27 are configured for press-fitting into a respectivecompartment of the cartridge shown in FIGS. 1 to 3. In particular thecross-sectional shape of each piston corresponds to the cross-sectionalshape of the respective compartment. However the pistons 26, 27 arepreferably oversized, in particular two-dimensionally enlarged by anoffset, relative to the cross-sectional shape of the respectivecompartment.

Each piston 26/27 has a skirt-type lip seal 26a/27a respectively. In theexample each lip seal 26 a/27 a protrudes from a front face 26 b/27 b ofthe piston 26/27 and forms a circumferential sealing edge at its frontmost end. The shape of the sealing edge corresponds to atwo-dimensionally enlarged shape of the cross-sectional shape of therespective compartment. Thus the lip seal 26/27 is adapted to form apress fit with the cartridge wall forming the compartment in which thepiston 26/27 is received. Accordingly the lip seal 26/27 is adapted toform a tight seal with the cartridge wall forming the compartment. Inthe example the lip seal 26/27 protrudes substantiallyfunnel-shaped—although at a substantial D-shaped cross-section—with thefunnel opening toward the free end of the lip seal 26/27. For use thepiston 26/27 is preferably assembled within the respective compartmentof the cartridge with the lip seal 26/27 oriented toward the respectivecomponent stored in the compartment. Accordingly pushing the piston26/27 toward the component for dispensing the component causes thecomponent to be pressurized and due to the pressure built up in thecomponent the lip seal is preferably urged toward the cartridge wallthat forms the compartment. Thus increasing pressure exerted to thecomponent during pushing the piston 26/27 preferably causes the sealeffect to increase. Therefore leakage during dispensation may beminimized. Further it has been found that due to the cross-sectionalshape of the lip seal based on only circular segments a sealing effect(see arrows in the Figure) is provided along the entire circumference ofthe to a D-shaped lip seal having a cross-sectional shape whichcomprises a straight section. The straight section of the lip seal maytoward its middle portion—depending on the pressure built up in thecomponent—provide only a small sealing effect or may even fail toprovide any sealing effect so that leakage may occur. Such insufficientsealing effect may particularly occur during storage of a cartridgeduring which the pressure, if any, within the compartments is low oreven an underpressure is created due to temperature variations.Therefore the invention helps maximizing the sealing effect between apiston and a cartridge that are based on a substantially D-shapedconfiguration.

1. A cartridge for storing and dispensing a two-component dentalmaterial, comprising: two compartments each extending within thecartridge at a cross-section which substantially corresponds to aD-shape, wherein the perimeter of the D-shape is defined by a pluralityof circle segments only, and wherein at least two of the circle segmentsare based on different definite radii.
 2. The cartridge of claim 1,wherein the circle segments join each other at their ends such that allcircle segments together form a closed line defining the perimeter ofthe compartment cross-section.
 3. The cartridge of claim 2, wherein thecircle segments join such that respective tangents on the two circlesegments through the joint coincide.
 4. The cartridge of claim 2,wherein the perimeter of the compartment cross-section is defined byonly a first, second, third and fourth circle segment, and wherein thefirst and second circle segment being based on different radii and joinat one of their ends with the third circle segment and join on the otherof their ends with the fourth circle segment.
 5. The cartridge of claim4, wherein the third and the fourth circle segment are based on the sameradius that is smaller than the radius of each of the first and secondcircle segment.
 6. The cartridge of claim 1, further comprising at afront portion an outlet for each of the compartments for extruding oneof the two components from the cartridge and a rear portion opposite ofthe front portion, wherein the rear portion is configured to receive apiston within the compartment.
 7. A piston for dispensing a component ofa dental material, having a cross-section which substantiallycorresponds to a D-shape, wherein the perimeter of the D-shape isdefined by a plurality of circle segments only, wherein at least two ofthe circle segments are based on different radii.
 8. The piston of claim7, wherein the circle segments join each other at their ends such thatall circle segments together form a closed line defining the perimeterof the compartment cross-section.
 9. The piston of claim 8, wherein thecircle segments are concatenated such that at the joint of two circlesegments respective tangents through that joint on each circle segmentcoincide.
 10. The piston of claim 8, wherein the perimeter of the pistoncross-section is defined by only a first, second, third and fourthcircle segment, the first and second circle segment being based ondifferent radii and join at one of their ends with the third circlesegment and join on the other of their ends with the fourth circlesegment.
 11. The piston of claim 10, wherein the third and the fourthcircle segment are based on the same radius that is smaller than theradius of each of the first and second circle segment.
 12. The piston ofany of claim 7, comprising a flexible sealing lip which forms theperimeter of the piston's cross-section.
 13. A syringe comprising acartridge of claim 1 and two pistons for dispensing components of adental material, wherein each piston has a cross-section, whichsubstantially corresponds to a D-shape, wherein the perimeter of theD-shape is defined by a plurality of circle segments only, and whereinat least two of the circle segments are based on different radii. 14.The syringe of claim 13, further comprising a dispensing nozzle and astatic mixer arranged in the dispensing nozzle and being configured tomix the two components as they are dispensed through the dispensingnozzle.
 15. The syringe of claim 14, further comprising a plunger forpushing the pistons into the respective compartments for extruding thecomponents towards the dispensing nozzle.